There may have a few problems with update & creating theme in Magento 2. To prevent all of that, I would like to show you a complete step-to-step tutorial with how to deal with Magento 2 theme.
In this post, I will show you first with ” How to create sample of Custom Theme in Magento 2″.

then add 1 more text as example below:<div class=”infor”>Hey, this is my theme.</div>

And then, go to Detail product page and Reload, you can see that “text“ in the “Add to cart” area.

And that is my simple method of creating a Custom Theme.
Wish you success with this tutorial.
In our Blog, we also write an article for who don’t have enough time to write a Magento 2 themes. Instead, they’ll want to choose a premium (and free) built by well-known brands in Magento field. Take a look if you’re one of them. And of course, please feel free to find more Magento 2 Tutorials by our Experts.